ETX TECHNICAL TIPS Last updated: 31 October 2003

Removable mount for Red Dot Finder

Sent:	Wednesday, October 29, 2003 18:48:45
From:	daniel.grabenstein@verizon.net (Dan Grabenstein)
After modifying my Crosman Red Dot Finder to reduce the dot intensity I
built a removable mount for my ETX 70AT.  All the parts were purchased
at the loval Home Depot, and include:

  a.. 4" coupling ( styrene ) SKU 52063 40405    $ 2.58
  b.. Aluminum plate 1/8 x 3/4 x 36 " SKU 30699 44710      $ 2.79
  c.. 2 ea 3/16 x 3/4 " Aluminum Binding Posts SKU 30699 43901        $ 1.72
  d.. 4 x 4 " Velcro sets ( w/ adhesive back ) ( I had on hand )    about $ 2
  e.. 14 " Multi purpose Ties SKU 728494151489 ( pkg of 8 )         $ 1.55

Slice a section about 2 to 2 1/2 " out of the coupling.  It has a ridge
in the inside dividing it approximately in half.  I shaved the ends of
the ridge so it would fit the curvature of the OTA better.

Drill two 3/16 " holes about 1 1/2 to 2 " apart and push the long piece
of the binding post in each hole.  The fit was tight enough that I
didn't bother to cement them in.  Cut a piece of the thicker part of the
velcro set to fit each half of the coupling arc and attach the velcro
covering the head of the binding post.

Cut a 1 1/2 to 2 " long piece of the aluminum plate and drill two  1/8 "
holes along the center line of the plate.  I used an 8-32 tap to thread
one of the holes and reamed out the other hole with a rat tail file in
order not th have to drill the holes with great precision. ( it was
easier to drill the holes in the approximate location of the binding
posts and ream one to make a good fit )  Rather than use the large head
screw that came with the binding post, I used a standard 8-32 x 3/4 "
screw.  This makes it easier to mount the Crosman finder using its own
mounting hardware.

The next step is to mount the Crosman on the plate.  Since the plate is
3/4 " wide I had to replace the 3/4 " long screws that came with the
Crosman with 1" long screws.

The mating piece of velcro is attached to the ETX OAT directly in front
of the eyepiece.  Simply using the velcro attachment holds the Crosman
securely to the OTA, but it has a lot of "slop".  In order to firmly
mount it in place use the 14" tie, one in front and one in the rear. 
Doing this the Red Dot Finder is quite firmly mounted, and with the 3/4
" high binding posts, you can sight through it with the 25mm eyepiece
mounted.

You can see the finished product mounted and up close in the attached
pictures.

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